Neutron capture therapy system and target for particle beam generating device

ABSTRACT

A neutron capture therapy system and a target for a particle beam generating device, which may improve the heat dissipation performance of the target, reduce blistering and extend the service life of the target. The neutron capture therapy system includes a neutron generating device and a beam shaping assembly. The neutron generating device includes an accelerator and a target, and a charg\ed particle beam generated by acceleration of the accelerator interacts with the target to generate a neutron beam. The target includes an acting layer, a backing layer and a heat dissipating structure, the acting layer interacts with the charged particle beam to generate the neutron beam, the backing layer supports the action layer, and the heat dissipating structure includes a tubular member composed of tubes arranged side by side.

RELATED APPLICATION INFORMATION

This application is a continuation of U.S. patent application Ser. No.16/513,956, filed on Jul. 17, 2019, which is a continuation of U.S.patent application Ser. No. 16/412,762, filed on May 15, 2019, which isa continuation of International Application No. PCT/CN2017/092742, filedon Jul. 13, 2017, which claims priority to Chinese Patent ApplicationNo. 201611213272.5, filed on Dec. 23, 2016; Chinese Patent ApplicationNo. 201621425423.9, filed on Dec. 23, 2016; Chinese Patent ApplicationNo. 201710389070.4, filed on May 26, 2017; Chinese Patent ApplicationNo. 201720599511.9, filed on May 26, 2017; Chinese Patent ApplicationNo. 201710384698.5, filed on May 26, 2017; Chinese Patent ApplicationNo. 201720600916.X, filed on May 26, 2017; Chinese Patent ApplicationNo. 201710384408.7, filed on May 26, 2017; Chinese Patent ApplicationNo. 201720599639.5, filed on May 26, 2017; Chinese Patent ApplicationNo. 201710383772.1, filed on May 26, 2017; Chinese Patent ApplicationNo. 201720599162.0, filed on May 26, 2017; Chinese Patent ApplicationNo. 201710389061.5, filed on May 26, 2017; and Chinese PatentApplication No. 201720600026.9, filed on May 26, 2017, the disclosuresof which are hereby incorporated by reference.

FIELD OF THE DISCLOSURE

One aspect of the present disclosure relates to a irradiation system, inparticular to a neutron capture therapy system; and another aspect ofthe present disclosure relates to a target for a irradiation system, inparticular to a target for a particle beam generating device.

BACKGROUND OF THE DISCLOSURE

As atomics moves ahead, such radiotherapy as Cobalt-60, linearaccelerators and electron beams has been one of major means to cancertherapy. However, conventional photon or electron therapy has beenundergone physical restrictions of radioactive rays; for example, manynormal tissues on a beam path will be damaged as tumor cells aredestroyed. On the other hand, sensitivity of tumor cells to theradioactive rays differs greatly, so in most cases, conventionalradiotherapy falls short of treatment effectiveness on radioresistantmalignant tumors (such as glioblastoma multiforme and melanoma).

For the purpose of reducing radiation damage to the normal tissuesurrounding a tumor site, target therapy in chemotherapy has beenemployed in the radiotherapy. While for high-radioresistant tumor cells,radiation sources with high RBE (relative biological effectiveness)including such as proton, heavy particle and neutron capture therapyhave also developed. Among them, the neutron capture therapy combinesthe target therapy with the RBE, such as the boron neutron capturetherapy (BNCT). By virtue of specific grouping of boronatedpharmaceuticals in the tumor cells and precise neutron beam regulation,BNCT is provided as a better cancer therapy choice than conventionalradiotherapy.

In the accelerator-based boron neutron capture therapy, the proton beamis accelerated by the accelerator to an energy sufficient to overcomethe nuclear coulomb repulsion of the target, and undergoes a nuclearreaction with the target to generate neutrons. Therefore, in the processof generating neutrons, the target is irradiated by an acceleratedproton beam of a very high energy level, the temperature of the targetis greatly increased, and the metal portion of the target is easilyblistered, thereby it may affect the service life of the target.

Therefore, it is necessary to propose a new technical solution to solvethe above problems.

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

SUMMARY

In order to solve the above problems, an aspect of the presentdisclosure provides a neutron capture therapy system including a neutrongenerating device and a beam shaping assembly, the neutron generatingdevice includes an accelerator and a target, and a charged particle beamgenerated by acceleration of the accelerator interacts with the targetto generate a neutron beam, the beam shaping assembly includes areflector, a moderator, a thermal neutron absorber, a radiation shield,and a beam exit, the moderator decelerates the neutron generated fromthe target to the epithermal neutron energy region, the reflectorsurrounds the moderator and directs the deviating neutron back to themoderator to enhance intensity of the epithermal neutron beam, thethermal neutron absorber is provided to absorb thermal neutrons to avoidoverdosing in superficial normal tissue during therapy, the radiationshield is arranged at the rear of the reflector around the beam exit,wherein the radiation shield is provided for shielding leaking neutronsand photons so as to reduce dose of the normal tissue in non-irradiatedarea, the target includes an acting layer, a backing layer and a heatdissipating structure, the acting layer interacts with the chargedparticle beam to generate the neutron beam, the backing layer supportsthe acting layer, and the heat dissipating structure includes a tubularmember composed of tubes arranged side by side. Use of the tubularmember as the heat dissipating structure increases the heat dissipationsurface, improves the heat dissipation effect, and helps to extend theservice life of the target.

Another aspect of the present disclosure provides a target for aparticle beam generating device, the target includes an acting layer, abacking layer and a heat dissipating structure, the acting layer isprovided for generating a particle beam, the backing layer supports theacting layer, and the heat dissipating structure includes a tubularmember composed of tubes arranged side by side. Use of the tubularmember as the heat dissipating structure increases the heat dissipationsurface, improves the heat dissipation effect, and helps to extend theservice life of the target.

In yet another aspect of the present disclosure provides a target for aneutron beam generating device, the target includes an acting layer anda backing layer, the acting layer is capable of interacting with anincident particle beam to generate the neutron beam, the backing layeris capable of both suppressing blistering caused by the incidentparticle beam and supporting the acting layer, the acting layer includesa first acting layer and a second acting layer, and the incidentparticle beam sequentially penetrates through the first acting layer andthe second acting layer in the incident direction. The neutron yield maybe increased by using the first acting layer and the second acting layerdisposed along the incident direction of the particle beam.

The fourth aspect of the present disclosure provides a neutron capturetherapy system, including a neutron generating device and a beam shapingassembly, the neutron generating device includes an accelerator and atarget, and a charged particle beam generated by acceleration of theaccelerator interacts with the target to generate a neutron beam, thebeam shaping assembly includes a reflector, a moderator, a thermalneutron absorber, a radiation shield, and a beam exit, the moderatordecelerates the neutron generated from the target to the epithermalneutron energy region, the reflector surrounds the moderator and directsthe deviating neutron back to the moderator to enhance intensity of theepithermal neutron beam, the thermal neutron absorber is provided toabsorb thermal neutrons to avoid overdosing in superficial normal tissueduring therapy, the radiation shield is arranged at the rear of thereflector around the beam exit for shielding leaking neutrons andphotons so as to reduce dose of the normal tissue in non-irradiatedarea, the target includes an acting layer and a backing layer, theacting layer is capable of interacting with the incident particle beamto generate the neutron beam, the backing layer is capable of bothsuppressing blistering caused by the incident particle beam andsupporting the acting layer, the acting layer includes a first actinglayer and a second acting layer, and the incident particle beamsequentially penetrates through the first acting layer and the secondacting layer in the incident direction. The neutron yield may beincreased by using the first acting layer and the second acting layerdisposed along the incident direction of the particle beam.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a neutron capture therapy system accordingto an embodiment of the present disclosure.

FIG. 2 is a schematic top view of a target according to an embodiment ofthe present disclosure.

FIGS. 3A and 3B are partially enlarged schematic views of the target ofFIG. 2, where FIG. 3A shows a tube and respective portions of layersdisposed on the tube, and

FIG. 3B shows two adjacent tubes as well as the respective portions oflayers disposed on the tube and the portions of layers forming theconnecting portion.

FIG. 4 is a schematic side view of the heat dissipating layer of thetarget of FIG. 2 as seen from direction A.

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure. Correspondingreference numerals indicate corresponding parts throughout the severalviews of the drawings.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described in furtherdetail with reference to the accompanying drawings in order to enablethose skilled in the art to practice with reference to the teachings.

As shown in FIG. 1, the neutron capture therapy system in thisembodiment is a boron neutron capture therapy system 100, which includesa neutron generating device 10, a beam shaping assembly 20, a collimator30, and a treatment table 40. The neutron generating device 10 includesan accelerator 11 and a target T, and the accelerator 11 acceleratescharged particles (such as protons, deuterons, etc.) to generate acharged particle beam P such as a proton beam, and the charged particlebeam P irradiates the target T and interacts with the target T togenerate a neutron beam N, and the target T is a metal target. Suitablenuclear reactions are always determined according to suchcharacteristics as desired neutron yield and energy, availableaccelerated charged particle energy and current and materialization ofthe metal target, among which the most discussed two are ⁷Li (p, n) ⁷Beand ⁹Be (p, n)⁹B and both are endothermic reaction. Their energythresholds are 1.881 MeV and 2.055 MeV respectively. Epithermal neutronsat a keV energy level are considered ideal neutron sources for BNCT.Theoretically, bombardment with lithium target using protons with energyslightly higher than the thresholds may produce neutrons relatively lowin energy, so the neutrons may be provided clinically without manymoderations. However, Li (lithium) and Be (beryllium) and protons ofthreshold energy exhibit not high action cross section. In order toproduce sufficient neutron fluxes, high-energy protons are usuallyselected to trigger the nuclear reactions. The target, consideredperfect, is supposed to have the advantages of high neutron yield, aproduced neutron energy distribution near the epithermal neutron energyrange (see details thereinafter), little strong-penetration radiation,safety, low cost, easy accessibility, high temperature resistance etc.But in reality, no nuclear reactions may satisfy all requests. However,well known by those skilled in the art, the target materials may be madeof other metals besides lithium or beryllium, for example, tantalum (Ta)or tungsten (W). The accelerator 11 may be a linear accelerator, acyclotron, a synchrotron, a synchrocyclotron.

The neutron beam N generated by the neutron generating device 10sequentially passes through the beam shaping assembly 20 and thecollimator 30 and then irradiates to the patient 200 on the treatmenttable 40. The beam shaping assembly 20 is capable of adjusting the beamquality of the neutron beam N generated by the neutron generating device10, and the collimator 30 is provided to concentrate the neutron beam N,so that the neutron beam N has higher targeting during the treatmentprocess. The beam shaping assembly 20 further includes a reflector 21, amoderator 22, a thermal neutron absorber 23, a radiation shield 24, anda beam exit 25. The neutrons generated by the neutron generating device10 have a wide spectrum of energy, and in addition to epithermalneutrons to meet treatment needs, it is desirable to reduce other typesof neutrons and photons as much as possible to avoid injury to operatorsor patients. Therefore, the neutrons coming out of the neutrongenerating device 10 need to pass through the moderator 22 to adjust theenergy of fast neutrons therein to the epithermal neutron energy region.The moderator 22 is made of a material having a cross section forprincipally acting with fast neutrons but hardly acting with epithermalneutrons. In this embodiment, the moderator 22 is made of at least oneof D₂O, AlF₃, Fluental, CaF₂, Li₂CO₃, MgF₂ and Al₂O₃. The reflector 21surrounds the moderator 22, and reflects the neutrons diffused throughthe moderator 22 back to the neutron beam N to improve the utilizationof the neutrons, and is made of a material having high neutronreflection ability. In this embodiment, the reflector 21 is made of atleast one of Pb or Ni. A thermal neutron absorber 23, which is made of amaterial having a large cross section for acting with thermal neutrons,is at the rear of the moderator 22. In this embodiment, the thermalneutron absorber 23 is made of Li-6. The thermal neutron absorber 23 isprovided to absorb the thermal neutrons passing through the moderator 22to reduce the content of thermal neutrons in the neutron beam N, therebyavoiding overdosing in superficial normal tissues during treatment. Aradiation shield 24 is disposed at the rear of the reflector around thebeam exit 25 for shielding neutrons and photons that leak from portionsother than the beam exit 25. The material of the radiation shield 24includes at least one of a photon shielding material and a neutronshielding material. In this embodiment, the material of the radiationshield 24 includes a photon shielding material lead (Pb) and a neutronshielding material polyethylene (PE). It should be appreciated that thebeam shaping assembly 20 may have other configurations as long as theepithermal neutron beam required for treatment may be obtained. Thecollimator 30 is disposed at the rear of the beam exit 25, and theepithermal neutron beam emerging from the collimator 30 irradiates tothe patient 200, and is slowed into thermal neutrons to reach the tumorcell M after passing through the superficial normal tissue. It should beunderstood that the collimator 30 may also be cancelled or replaced byother structures, and the neutron beam from the beam exit 25 is directlyirradiated to the patient 200. In this embodiment, a radiation shieldingdevice 50 is disposed between the patient 200 and the beam exit 25 toshield the radiation from the beam exit 25 to the normal tissue of thepatient. It should be understood that the radiation shielding device 50may also not be provided.

After the patient 200 is administrated or injected boron(B-10)-containing pharmaceuticals, the boron-containing pharmaceuticalsselectively accumulates in the tumor cell M, and then takes advantagethat the boron (B-10)-containing pharmaceuticals have high neutroncapture cross section and produces ⁴He and ⁷Li heavy charged particlesthrough ¹⁰B(n,α)⁷Li neutron capture and nuclear fission reaction. Thetwo charged particles, with average energy at about 2.33 MeV, are ofhigh linear energy transfer (LET) and short-range characteristics. LETand range of the alpha particle are 150 keV/micrometer and 8 micrometersrespectively while those of the heavy charged particle ⁷Li are 175keV/micrometer and 5 micrometers respectively, and the total range ofthe two particles approximately amounts to a cell size. Therefore,radiation damage to living organisms may be restricted at the cells'level. Only the tumor cells will be destroyed on the premise of havingno major normal tissue damage.

The structure of the target T will be described in detail below withreference to FIGS. 2, 3A, 3B and 4.

The target T is disposed between the accelerator 11 and the beam shapingassembly 20, and the accelerator 11 has an accelerating tube 111 thataccelerates the charged particle beam P. In this embodiment, theaccelerating tube 111 penetrates into the beam shaping assembly 20 inthe direction of the charged particle beam P, and sequentially passesthrough the reflector 21 and the moderator 22. The target T is arrangedinto the moderator 22 and located at the end of the accelerating tube111 to obtain a better neutron beam quality.

The target T includes a heat dissipating structure 12, a backing layer13 and an acting layer 14, the acting layer 14 interacts with thecharged particle beam P to generate a neutron beam, and the backinglayer 13 supports the acting layer 14. In this embodiment, the materialof the acting layer 14 is Li or an alloy thereof, the charged particlebeam P is a proton beam. The target T further includes an anti-oxidationlayer 15 (also known as an oxidation resistant layer) on one side of theacting layer 14 for preventing oxidation of the acting layer, thebacking layer 13 may simultaneously suppress blistering caused by theincident proton beam. The charged particle beam P sequentiallypenetrates through the oxidation resistant layer 15, the acting layer14, and the backing layer 13 in the incident direction. The material ofthe oxidation resistant layer 15 is considered to be less susceptible tocorrosion by the acting layer and may reduce the loss of the incidentproton beam and the heat generated by the proton beam at the same time,such as at least one of Al, Ti and an alloy thereof or stainless steel.In this embodiment, the material of the anti-oxidation layer 15 iscapable of undergoing nuclear reaction with protons at the same time,which may further increase the neutron yield while performing theabove-mentioned functions. At this time, the anti-oxidation layer isalso a part of the acting layer, the material of the anti-oxidationlayer 15 may be Be or an alloy thereof. The energy of the incidentproton beam is higher than the energy threshold of the nuclear reactionwith Li and Be, which may result in two different nuclear reactions, ⁷Li(p, n) ⁷Be and ⁹Be (p, n)⁹B. In addition, Be has a high melting pointand good thermal conductivity, and its melting point is 1287° C.,thermal conductivity is 201 W/(m K). Be has great advantage over Li (amelting point of 181° C., a thermal conductivity of 71 W/(m K)) in hightemperature resistance and heat dissipation, which may further increasethe service life of the target. The reaction threshold of Be and protonfor (p, n) nuclear reaction is about 2.055 MeV, the energy of mostaccelerator-based neutron sources using proton beams is above thereaction threshold, and beryllium target is also the best choice inaddition to lithium target. The neutron yield is improved due to thepresence of Be compared to the antioxidant layer using other materialssuch as Al. In this embodiment, the proton beam energy is 2.5 MeV-5 MeV,which may produce a high action cross section with the lithium target,and not generate excessive fast neutrons simultaneously, thus obtainsbetter beam quality. The acting layer 14 reacts sufficiently with theprotons with a thickness of 80 μm-240 μm, and may not cause excessiveenergy deposition due to big thickness, which may affect the heatdissipation performance of the target. To achieve the above effects withlow manufacturing cost ensured, the oxidation resistant layer 15 has athickness of 5 μm-25 μm. In the comparative experiment, Monte Carlosoftware was provided to simulate the proton beams of 2.5 MeV, 3 MeV,3.5 MeV, 4 MeV, 4.5 MeV, and 5 MeV respectively, which were sequentiallypenetrated into the anti-oxidation layer 15, the acting layer 14 (Li)and backing layer 13 (Ta, which will be described later) in a directionperpendicular to the active surface of the target T. The material of theoxidation resistant layer 15 is compared between Al and Be. Theanti-oxidation layer 15 has a thickness of 5 μm, 10 μm, 15 μm, 20 μm, 25μm, respectively, and the acting layer 14 has a thickness of 80 μm, 120μm, 160 μm, 200 μm, 240 μm, respectively, and the thickness of thebacking layer 12 has little effect on the neutron yield and may beadjusted according to the actual situation. The obtained neutron yield(i.e., the number of neutrons generated per proton) is shown in Tables 1and 2. The calculation results of the neutron yield increase ratio ofusing Be as antioxidant layer of the lithium target with respect to Alare shown in Table 3. From the results, it was found that when Be wasprovided as the anti-oxidation layer material, the neutron yield wassignificantly increased relative to Al, and the neutron yield obtainedwas 7.31E-05 n/proton −5.61E-04 n/proton.

TABLE 1 Neutron yield (n/proton) using Al as antioxidant layer of thelithium target. E is energy of the incident proton Thickness of Li (μm)E (MeV) 80 120 160 200 240  5 μm Al 2.5 1.32E−04 1.32E−04 1.32E−041.32E−04 1.32E−04 3 1.15E−04 2.06E−04 2.61E−04 2.62E−04 2.62E−04 3.51.15E−04 1.69E−04 2.26E−04 2.99E−04 3.81E−04 4 1.28E−04 1.90E−042.49E−04 3.04E−04 3.58E−04 4.5 1.53E−04 2.21E−04 2.88E−04 3.51E−044.11E−04 5 2.03E−04 2.94E−04 3.77E−04 4.51E−04 5.20E−04 10 μm Al 2.58.26E−05 8.26E−05 8.26E−05 8.26E−05 8.26E−05 3 1.31E−04 2.11E−042.35E−04 2.35E−04 2.35E−04 3.5 1.12E−04 1.66E−04 2.27E−04 3.18E−043.71E−04 4 1.26E−04 1.86E−04 2.43E−04 2.97E−04 3.52E−04 4.5 1.46E−042.13E−04 2.77E−04 3.39E−04 4.00E−04 5 1.99E−04 2.87E−04 3.64E−044.34E−04 5.02E−04 15 μm Al 2.5 3.78E−05 3.78E−05 3.78E−05 3.78E−053.78E−05 3 1.54E−04 2.06E−04 2.07E−04 2.07E−04 2.07E−04 3.5 1.09E−041.66E−04 2.42E−04 3.21E−04 3.43E−04 4 1.25E−04 1.83E−04 2.38E−042.91E−04 3.50E−04 4.5 1.41E−04 2.08E−04 2.72E−04 3.33E−04 3.91E−04 51.91E−04 2.72E−04 3.45E−04 4.15E−04 4.82E−04 20 μm Al 2.5 8.89E−068.89E−06 8.89E−06 8.89E−06 8.88E−06 3 1.57E−04 1.77E−04 1.77E−041.77E−04 1.77E−04 3.5 1.09E−04 1.72E−04 2.62E−04 3.12E−04 3.13E−04 41.22E−04 1.78E−04 2.31E−04 2.87E−04 3.55E−04 4.5 1.36E−04 2.01E−042.62E−04 3.22E−04 3.78E−04 5 1.82E−04 2.60E−04 3.32E−04 3.99E−044.65E−04 25 μm Al 2.5 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 31.40E−04 1.40E−04 1.40E−04 1.40E−04 1.40E−04 3.5 1.10E−04 1.89E−042.66E−04 2.84E−04 2.84E−04 4 1.19E−04 1.73E−04 2.27E−04 2.87E−043.73E−04 4.5 1.34E−04 1.97E−04 2.57E−04 3.15E−04 3.70E−04 5 1.72E−042.46E−04 3.14E−04 3.80E−04 4.44E−04

TABLE 2 Neutron yield (n/proton) using Be as antioxidant layer of thelithium target. E is energy of the incident proton Thickness of Li (μm)E (MeV) 80 120 160 200 240  5 μm Be 2.5 1.46E−04 1.46E−04 1.46E−041.46E−04 1.46E−04 3 1.21E−04 2.11E−04 2.74E−04 2.80E−04 2.80E−04 3.51.26E−04 1.79E−04 2.35E−04 3.05E−04 3.92E−04 4 1.45E−04 2.06E−042.65E−04 3.21E−04 3.74E−04 4.5 1.73E−04 2.42E−04 3.08E−04 3.71E−044.33E−04 5 2.23E−04 3.16E−04 4.00E−04 4.75E−04 5.44E−04 10 μm Be 2.51.12E−04 1.12E−04 1.12E−04 1.12E−04 1.12E−04 3 1.37E−04 2.26E−042.64E−04 2.64E−04 2.64E−04 3.5 1.33E−04 1.87E−04 2.46E−04 3.31E−043.99E−04 4 1.57E−04 2.17E−04 2.75E−04 3.29E−04 3.84E−04 4.5 1.86E−042.54E−04 3.19E−04 3.81E−04 4.42E−04 5 2.41E−04 3.29E−04 4.10E−044.82E−04 5.50E−04 15 μm Be 2.5 7.31E−05 7.31E−05 7.31E−05 7.31E−057.31E−05 3 1.66E−04 2.37E−04 2.51E−04 2.51E−04 2.51E−04 3.5 1.39E−041.94E−04 2.60E−04 3.51E−04 3.93E−04 4 1.67E−04 2.26E−04 2.82E−043.36E−04 3.93E−04 4.5 2.02E−04 2.69E−04 3.32E−04 3.94E−04 4.54E−04 52.55E−04 3.40E−04 4.17E−04 4.88E−04 5.54E−04 20 μm Be 2.5 4.38E−054.38E−05 4.38E−05 4.38E−05 4.38E−05 3 1.89E−04 2.37E−04 2.38E−042.38E−04 2.38E−04 3.5 1.48E−04 2.06E−04 2.85E−04 3.61E−04 3.80E−04 41.78E−04 2.36E−04 2.92E−04 3.45E−04 4.05E−04 4.5 2.18E−04 2.83E−043.45E−04 4.06E−04 4.65E−04 5 2.70E−04 3.51E−04 4.23E−04 4.92E−045.59E−04 25 μm Be 2.5 2.12E−05 2.12E−05 2.12E−05 2.12E−05 2.12E−05 31.98E−04 2.22E−04 2.22E−04 2.22E−04 2.22E−04 3.5 1.56E−04 2.18E−043.10E−04 3.63E−04 3.65E−04 4 1.89E−04 2.46E−04 3.00E−04 3.55E−044.21E−04 4.5 2.34E−04 2.98E−04 3.59E−04 4.20E−04 4.76E−04 5 2.81E−043.59E−04 4.29E−04 4.96E−04 5.61E−04

TABLE 3 The neutron yield increase ratio of using Be as antioxidantlayer of the lithium target with respect to Al. E is energy of theincident proton Thickness of Li (μm) E (MeV) 80 120 160 200 240 5 μmBe-5 μm Al 2.5 11% 11% 11% 11% 11% 3  6%  2%  5%  7%  7% 3.5  9%  6%  4% 2%  3% 4 13%  9%  6%  5%  5% 4.5 13%  9%  7%  6%  5% 5 10%  7%  6%  5% 5% 10 μm Be-10 μm Al 2.5 36% 36% 36% 36% 36% 3  4%  7% 12% 12% 12% 3.519% 12%  8%  4%  7% 4 24% 17% 13% 11%  9% 4.5 28% 19% 15% 12% 11% 5 21%15% 13% 11% 10% 15 μm Be-15 μm Al 2.5 93% 93% 93% 93% 93% 3  8% 15% 22%22% 22% 3.5 28% 17%  7%  9% 15% 4 34% 24% 19% 15% 12% 4.5 44% 29% 22%18% 16% 5 34% 25% 21% 18% 15% 20 μm Be-20 μm Al 2.5 393%  393%  393% 393%  393%  3 20% 34% 34% 34% 34% 3.5 35% 20%  9% 16% 21% 4 46% 33% 26%20% 14% 4.5 60% 41% 32% 26% 23% 5 48% 35% 28% 23% 20% 25 μm Be-25 μm Al2.5 n/a n/a n/a n/a n/a 3 42% 58% 58% 58% 58% 3.5 42% 16% 17% 28% 29% 459% 42% 32% 24% 13% 4.5 75% 51% 40% 33% 29% 5 64% 46% 37% 31% 26%

The heat dissipating structure 12 is made of a heat conductive material(for example a material having good thermal conductivity such as Cu, Fe,Al, and the like) or a material capable of both heat conduction andblistering suppression; the backing layer 13 is made of a material thatsuppresses blistering; the material which suppresses blistering or whichis capable of both heat conduction and blistering suppression includesat least one of Fe, Ta or V. The heat dissipating structure may have avariety of configurations, such as a flat plate. In this embodiment, theheat dissipating structure 12 includes a tubular member 121 and asupport member 122. Both the tubular member 121 and the support member122 are made of Cu, which has better heat dissipation performance andlower cost. The tubular member 121 is composed of tubes arranged side byside and is positioned and mounted by the support member 122, and thesupport member 122 is fixed into the moderator 22 or to the end portionof the accelerating tube 111 by a connecting member such as a bolt or ascrew. It should be understood that other detachable connections may beprovided to facilitate the replacement of the target. The structure ofthe tubes increase the heat dissipation area, improve the heatdissipation effect, and help to extend the service life of the target.The heat dissipating structure 12 further has cooling channels P forpassing cooling medium. In this embodiment, the cooling medium is water,and the interior of the tubes constituting the tubular member 121 atleast partially forms the cooling passages P, and the cooling mediumflows through the interior of the tubes to carry away their heat. Theinterior of the tubes acts as cooling passages, which further enhancesthe heat dissipation effect and extends the service life of the target.The shape, number and size of the tubes are determined according to thesize of the actual target. Only four circular tubes are schematicallyillustrated in the drawings. It should be understood that they may alsobe square tubes, polygonal tubes, elliptical tubes or the like andcombinations thereof. Adjacent tubes may be next to each other such thattheir outer surfaces are in contact with each other or may be spacedapart. The cross-sectional shape of the inner bore of the tubes may alsobe varied, such as circular, polygonal, elliptical, and the like, anddifferent cross-sections may have different shapes. Since the diameterof each tube in the actual manufacturing of the tubular member is smalland there are cooling passages inside the tubular member, theconventional production process is difficult. In this embodiment,additive manufacturing is provided to obtain the tubular member tofacilitate the formation of small structures and complex structures.Firstly, the three-dimensional modeling of the tubular member is carriedout, and the three-dimensional model data of the tubular member is inputinto the computer system and layered into two-dimensional slice data.Then, the raw materials (such as copper powder) are layer-by-layermanufactured through a computer-controlled additive manufacturingsystem, and the three-dimensional products are finally obtained afterbeing superposed.

When the backing layer 13 is made of Ta, it has a certain heatdissipation effect and may reduce blistering, suppress inelasticscattering between protons and Li which releases y, and prevent excessprotons from penetrating through the target. In this embodiment, thematerial of the backing layer 13 is a Ta—W alloy, which maysignificantly improve the low strength and the poor thermal conductivityof the pure tantalum while maintaining the above excellent performanceof the Ta, so that the heat generated by the nuclear reaction of theacting layer 14 may be conducted out in time by the backing layer. Atthis time, the heat dissipating structure may also be at least partiallymade of the same material or integrated structured with the backinglayer. The weight percentage of W in the Ta—W alloy is 2.5%-20% toensure the blistering suppression property of the backing layer, and thebacking layer has higher strength and thermal conductivity, whichfurther extends the service life of the target. The Ta—W alloy such asTa-2.5 wt % W, Ta-5.0 wt % W, Ta-7.5 wt % W, Ta-10 wt % W, Ta-12 wt % W,Ta-20 wt % W, and the like is formed into a plate-like backing layer 13by powder metallurgy, forging, pressing, and the like. When the energyof the proton beam is 1.881 MeV-10 MeV, the thickness of the backinglayer is at least 50 μm to sufficiently absorb excess protons.

In this embodiment, the manufacturing process of the target T is asfollows:

S1: the liquid lithium metal is poured onto the backing layer 13 to formthe acting layer 14, and may also be treated by evaporation orsputtering, an extremely thin adhesion layer 16 may be disposed betweenlithium and tantalum, and the material of the adhesion layer 16 includesat least one of Cu, Al, Mg or Zn, and it may also be treated byevaporation or sputtering to improve the adhesion between the backinglayer and the acting layer;

S2: the backing layer 13 and the tubular member 121 of the heatdissipating structure 12 are subjected to HIP (Hot Isostatic Pressing)treatment;

S3: the oxidation resistant layer 15 is simultaneously subjected to HIPtreatment or by other processes to seal the backing layer 13 to form acavity and/or to surround the acting layer 14;

S4: the support member 122 and the tubular member 121 are connected bywelding, press fitting, or the like.

The above steps S1, S2, S3 and S4 are not in any order. For example, theanti-oxidation layer 15 and the backing layer 13 may be subjected to HIPtreatment or other processes to seal the backing layer 13 to form acavity, and liquid lithium metal is poured into the cavity to form theacting layer 14. It should be understood that the support member 122 mayalso be omitted, and the tubes may be connected and fixed in one pieceby welding or other means. The backing layer 13, the acting layer 14,and the anti-oxidation layer 15 on each tube are separately formed, andthen the tubular member is positioned and connected with the supportmember 122. After the connection, the entirety of the respectiveportions of the backing layer 13, the acting layer 14, and the oxidationresistant layer 15 formed on each of the tubes may be discontinuous, andit is necessary to form a connecting portion 17 between adjacent tubes(see FIG. 3B), and the connecting portion 17 is also composed of acorresponding portion of the backing layer 13, a corresponding portionof the acting layer 14, and a corresponding portion of the oxidationresistant layer 15. The entire target is divided into a plurality ofseparate functional portions, which further reduces the blistering ofthe metal antioxidant layer. At this time, the connection between thesupport member 122 and the tubular member 121 in S4 may also bedetachable, and the target T may be partially replaced to extend theservice life of the target and reduce the treatment cost of the patient.It should be understood that the backing layer 13, the acting layer 14,and the anti-oxidation layer 15 on each tube may also be integrallyformed and then connected to the tubular member, so that the actinglayer of the target T is continuous as a whole after the connection, andit is advantageous for the charged particle beam P to interact with thetarget T. At this time, the support member 122 and the tubular member121 may also be integrally obtained by additive manufacturing, whichreduces the difficulty in processing and assembly. The shape of thecross section of the entirety formed by the backing layer 13, the actinglayer 14, and the oxidation resistant layer 15 perpendicular to thecenter line of the tube may also be various, for example, it isconsistent with the outer surface contour of the side of the tubularmember connecting with the backing layer 13, the acting layer 14, andthe oxidation resistant layer 15. In this embodiment, it is arc shape,which increases the area in which the target T interacts with thecharged particle beam P and the area in which the heat dissipating layer12 contacts the backing layer 13 and conducts heat. The acting layer 14on each tube covers at least ¼ of the outer circumference of the tube,i.e., the central angle α of the portion of the outer circumference ofeach tube covered by the respective portion of the acting layer 14 is atleast 90 degrees.

In this embodiment, the support member 122 includes a first supportportion 1221 and a second support portion 1222 symmetrically disposed attwo ends of the tubular member 121, respectively having a cooling inletIN and a cooling outlet OUT, and the cooling passages P communicateswith the cooling inlet IN and cooling outlet OUT. The cooling passages Pincludes a first cooling passage P1 on the first support portion, asecond cooling passage P2 on the second support portion, and a thirdcooling passage P3 formed inside the tubes constituting the tubularmember 121. The cooling medium enters from the cooling inlet IN on thefirst support portion 1221, enters the interior of each of the tubesconstituting the tubular member 121 through the first cooling passageP1, and then exits from the cooling outlet OUT through the secondcooling passage P2 on the second support portion. The temperature of thetarget T is increased by irradiation with an accelerated proton beam ofa high energy level and generates heat, which is conducted by thebacking layer and the heat dissipating structure, and is carried out bycooling medium circulating in the tubular member and the support member,thereby cooling the target T.

It should be understood that the first cooling passage P1 and the secondcooling passage P2 may also adopt other arrangements, such as thecooling medium entering from the cooling inlet IN on the firstsupporting portion 1221 sequentially passes through the interior of therespective tubes constituting the tubular member 121, and finally exitsfrom the cooling outlet OUT on the second support portion. The coolingmedium may also directly enter and exit the tubular member withoutpassing through the support member. At this time, the cooling inlet INand the cooling outlet OUT may be disposed on the tubular 121, and therespective tubes are sequentially connected to form cooling passages P,and the cooling medium sequentially flows through the interior of eachtube.

The support member 122 may further include a third support portion 1223connecting the first and second support portions 1221, 1222, and thethird support portion 1223 is in contact with a second side (i.e., theright side as shown in FIG. 2) of the tubular member 121, which isopposite to the first side (i.e., the left side as shown in FIG. 2) ofthe tubular member 121 connecting with the acting layer 14, the thirdsupport portion 1223 may also have a fourth cooling passage thatconstitutes the cooling passages P. At this time, the cooling medium maypass only through the support member 122 without passing through theinterior of each tube of the tubular member 121, and the interior ofeach tube is not in communication with the cooling passages within thesupport member 122. The cooling passages in the support member 122 maybe arranged in a variety of ways, such as a spiral shape, as much aspossible through the area in contact with the tubes. The cooling mediummay also pass through both the interior of the tubes and the thirdsupport portion of the support member or both the interior of the tubeand the first, second and third support portions of the support member.

In this embodiment, first and second cooling pipes D1 and D2 aredisposed between the accelerating tube 111 and the reflector 21, andbetween the accelerating tube 111 and the moderator 22, and one end ofthe first and second cooling pipes D1, D2 is respectively connected tothe cooling inlet IN and the cooling outlet OUT of the target T, and theother ends are connected to an external cooling source. It should beunderstood that the first and second cooling tubes may also be disposedinto the beam shaping assembly in other ways, and may also be omittedwhen the target is placed outside the beam shaping assembly.

It should be understood that the heat dissipating structure 12 may alsobe simultaneously provided as the backing layer 13. At this time, theheat dissipating structure 12 is at least partially made of a materialcapable of both heat conduction and blistering suppression, for example,the tubular member 121 made of Ta or Ta—W alloy and the support member122 made of Cu. The acting layer 14 is connected to the Ta or Ta—W alloytube by a process such as evaporation or sputtering, and the Ta or Ta—Walloy tube serves as both the backing layer 13 and the heat dissipatingstructure 12. In this embodiment, the target T has a rectangular plateshape as a whole. It should be understood that the target T may also bein the shape of a disk, and the first support portion and the secondsupport portion constitute a whole circumference or a part of thecircumference, and the length of the tubes may be different at thistime. The target T may also be in other solid shapes. The target T mayalso be movable relative to the accelerator or the beam shaping assemblyto facilitate target replacement or to make the particle beam evenlyinteract with the target. A liquid material (liquid metal) may also beprovided for the acting layer 14.

It should be understood that the target of the present disclosure mayalso be applied to other neutron generating devices in the medical andnon-medical fields, as long as the generation of the neutron is based onthe nuclear reaction between the particle beam and the target, thematerial of the target is also differentiated based on different nuclearreactions. It may also be applied to other particle beam generatingdevices.

The “tubular member” in the present invention refers to a whole unitformed by a plurality of individual tubes arranged and connected by aconnecting member or a joining process, and an object having a hollowportion formed in one or more plate members or obtained by combining oneor more plate members may not to be understood as a tubular member ofthe present invention. The “tubular member” in the present inventionrefers to a whole unit formed by a plurality of individual tubesarranged and connected by a connecting member or a joining process, andan object having a hollow portion formed in one or more plate members orobtained by combining one or more plate members may not to be understoodas a tubular member of the present invention.

Although the illustrative embodiments of the present invention have beendescribed above in order to enable those skilled in the art tounderstand the present invention, it should be understood that thepresent invention is not to be limited the scope of the embodiments. Forthose skilled in the art, as long as various changes are within thespirit and scope as defined in the present invention and the appendedclaims, these changes are obvious and within the scope of protectionclaimed by the present invention.

What is claimed is:
 1. A neutron capture therapy system, comprising: aneutron generating device comprising an accelerator and a target,wherein a charged particle beam generated by acceleration of theaccelerator interacts with the target to generate a neutron beam,wherein the target comprises: an acting layer for interacting with thecharged particle beam to generate the neutron beam, a backing layer forsupporting the acting layer, wherein the acting layer is disposed on thebacking layer, and a heat dissipating structure including a tubularmember composed of tubes arranged side by side, wherein the acting layerand the backing layer are disposed on the tubular member such that arespective portion of the acting layer is disposed on each of the tubesof the tubular member, and a respective portion of the backing layer isdisposed between the respective portion of the acting layer and each ofthe tubes of the tubular member; and a beam shaping assembly comprising:a moderator for decelerating the neutron generated from the target tothe epithermal neutron energy region, a reflector surrounding themoderator, wherein the reflector directs the deviating neutron back tothe moderator to enhance intensity of the epithermal neutron beam, athermal neutron absorber provided to absorb thermal neutrons to avoidoverdosing in superficial normal tissue during therapy, a radiationshield arranged at the rear of the reflector around the beam exit forshielding leaking neutrons and photons so as to reduce dose of thenormal tissue in non-irradiated area, and a beam exit.
 2. The neutroncapture therapy system according to claim 1, wherein the chargedparticle beam is a proton beam, a material of the acting layer is Li oran alloy thereof, and the acting layer undergoes a ⁷Li (p, n) ⁷Benuclear reaction with the proton beam to generate neutrons; or thematerial of the acting layer is Be or an alloy thereof, and the actinglayer undergoes a ⁹Be (p, n)⁹B nuclear reaction with the proton beam togenerate neutrons.
 3. The neutron capture therapy system according toclaim 1, wherein the target further comprises an oxidation resistantlayer disposed on the acting layer, and a material of the oxidationresistant layer includes at least one of Al, Ti, Be and an alloy thereofor stainless steel, an adhesion layer is disposed between the actinglayer and the backing layer, and a material of the adhesion layerincludes at least one of Cu, Al, Mg, or Zn, the heat dissipatingstructure is made of a heat conductive material or a material for bothheat conduction and blistering suppression, the backing layer is made ofa material for suppressing blistering, the material for suppressingblistering or the material for both heat conduction and blisteringsuppression includes at least one of Fe, Ta or V, the heat dissipatingstructure and the backing layer are connected by a HIP process, and theacting layer and the backing layer are connected by a casting,evaporation or sputtering process.
 4. The neutron capture therapy systemaccording to claim 1, wherein a material of the backing layer is Ta—Walloy, and a mass percentage of W in the Ta—W alloy is 2.5% to 20%, anenergy of the charged particle beam is 1.881 MeV to 10 MeV, and athickness of the backing layer is at least 50 μm.
 5. The neutron capturetherapy system according to claim 1, wherein an outer surface contour ofa first side of the tubular member connected with the acting layer is inan arc shape, and the respective portion of the acting layer disposed oneach of the tubes of the tubular member covers at least ¼ of an outercircumference of each of the tubes, a central angle of a portion of theouter circumference of each of the tubes covered by the respectiveportion of the acting layer is at least 90 degrees.
 6. The neutroncapture therapy system according to claim 1, wherein the target furthercomprises an oxidation resistant layer disposed on the acting layer, anda portion of the backing layer and a portion of the acting layer notdisposed on each of the tubes and a portion of the oxidation resistantlayer disposed on the portion of the acting layer collectively form aconnecting portion between two adjacent ones of the tubes.
 7. Theneutron capture therapy system according to claim 1, wherein the heatdissipating structure further comprises a support member, a material ofthe support member is Cu, the tubular member and the support member arewelded or detachably connected or integrally formed by additivemanufacturing, and the support member and/or the tubular member comprisea cooling passage.
 8. The neutron capture therapy system according toclaim 7, wherein the support member comprises a first support portionand a second support portion disposed at both ends of the tubularmember, the support member further comprises a third support portionconnecting the first and second support portions, the third supportportion is in contact with a second side of the tubular member oppositeto the first side of the tubular member connected with the acting layer,and a cooling medium passes only through the support member, or boththrough an interior of each of the tubes of the tubular member and thethird support portion of the support member, or both through theinterior of each of the tubes and the first, second and third supportportions of the support member.
 9. The neutron capture therapy systemaccording to claim 8, wherein the first support portion comprises acooling inlet and a first cooling passage, the second support portioncomprises a cooling outlet and a second cooling passage, the coolingmedium enters the interior of each of the tubes of the tubular memberthrough the first cooling passage from the cooling inlet, and then exitsthe cooling outlet through the second cooling passage, and the coolingmedium is water.
 10. The neutron capture therapy system according toclaim 1, wherein the neutron capture therapy system further comprises atreatment table and a collimator, the neutron beam generated by theneutron generating device is irradiated to a patient on the treatmenttable through the beam shaping assembly, a radiation shielding device isdisposed between the patient and the beam exit to shield radiation fromthe beam exit to the normal tissue of the patient, the collimator isdisposed at a rear portion of the beam exit to converge the neutronbeam, and first and second cooling pipes are disposed in the beamshaping assembly, wherein the target has a cooling inlet, a coolingoutlet, and a cooling passage disposed between the cooling inlet and thecooling outlet, an end of each of the first and second cooling pipes isrespectively connected to the cooling inlet and the cooling outlet ofthe target, and the other ends are connected to an external coolingsource, and interior of each tube of the pipe-shaped member constitutesat least a portion of the cooling passage.
 11. The neutron capturetherapy system according to claim 10, wherein the target is locatedwithin the beam shaping assembly, the accelerator has an acceleratingtube that accelerates the charged particle beam, and the acceleratingtube extends into the beam shaping assembly in the direction of thecharged particle beam and sequentially penetrates through the reflectorand the moderator, the target is disposed in the moderator and locatedat end of the accelerating tube, and the first and second cooling pipesare disposed between the accelerating tube and the reflector, andbetween the accelerating tube and the moderator.
 12. A neutron capturetherapy system, comprising: a neutron generating device comprising anaccelerator and a target, wherein a charged particle beam generated byacceleration of the accelerator interacts with the target to generate aneutron beam, wherein the target comprises: an acting layer forinteracting with the charged particle beam to generate the neutron beam,wherein the acting layer comprises a first acting layer and a secondacting layer, and the charged particle beam sequentially penetratesthrough the first acting layer and the second acting layer in adirection of the charged particle beam, and a backing layer for bothsuppressing blistering caused by the charged particle beam andsupporting the acting layer, wherein the acting layer is disposed on thebacking layer; and a beam shaping assembly comprising: a moderator fordecelerating the neutron generated from the target to the epithermalneutron energy region, a reflector surrounding the moderator, whereinthe reflector directs the deviating neutron back to the moderator toenhance intensity of the epithermal neutron beam, a thermal neutronabsorber provided to absorb thermal neutrons to avoid overdosing insuperficial normal tissue during therapy, a radiation shield arranged atthe rear of the reflector around the beam exit for shielding leakingneutrons and photons so as to reduce dose of the normal tissue innon-irradiated area, and a beam exit.
 13. The neutron capture therapysystem according to claim 12, wherein materials of the first and secondacting layers are both materials for undergoing nuclear reaction withthe charged particle beam, and the materials of the first and secondacting layers are different.
 14. The neutron capture therapy systemaccording to claim 13, wherein the material of the first acting layer isBe or an alloy thereof, and the material of the second acting layer isLi or an alloy thereof, the charged particle beam is a proton beam, thefirst and second acting layers respectively undergo ⁹Be(p, n) ⁹B and⁷Li(p, n) ⁷Be reaction with the proton beam to generate neutrons, anenergy of the proton beam is 2.5 MeV-5 MeV, and a neutron yield is7.31E-05 n/proton −5.61E-04 n/proton.
 15. The neutron capture therapysystem according to claim 12, wherein the first acting layer has athickness of 5 μm to 25 μm, and the second acting layer has a thicknessof 80 μm to 240 μm.
 16. The neutron capture therapy system according toclaim 12, wherein the second acting layer and the backing layer areconnected by a casting, evaporation or sputtering process, and the firstacting layer seals the backing layer to form a cavity and/or surroundsthe second acting layer by HIP processing.
 17. The neutron capturetherapy system according to claim 12, wherein an adhesion layer isdisposed between the second acting layer and the backing layer, and amaterial of the adhesion layer includes at least one of Cu, Al, Mg, orZn.
 18. The neutron capture therapy system according to claim 12,wherein the target further comprises a heat dissipating structurecomprising a cooling passage formed by additive manufacturing.
 19. Theneutron capture therapy system according to claim 18, wherein thebacking layer is made of a material for suppressing blistering, and theheat dissipating layer is made of a heat conductive material or amaterial capable of both heat conduction and blistering suppression, thematerial for suppressing blistering or the material capable of both heatconduction and blistering suppression comprises at least one of Fe, Taor V, and the heat conductive material comprises at least one of Cu, Fe,and Al, the heat dissipating layer and the backing layer are connectedby a HIP process.
 20. The neutron beam generating device according toclaim 18, wherein the heat dissipating structure and the backing layerare at least partially of the same material or integrated, and the samematerial is Ta or a Ta—W alloy.